Downy mildew continues to take a toll on cucumbers and melons throughout the state. We have numerous reports of downy mildew on these two crops from northern and central Ohio, with new observations confirmed yesterday in Hardin and Greene counties. Downy mildew is best managed by preventative fungicide applications – a list of effective fungicides can be found in my June 28, 2017 post.
We still have not confirmed downy mildew on pumpkins or squash anywhere in Ohio. However, downy mildew has been reported on butternut squash in Blair County in central PA, and on jack-o-lantern pumpkins in Starke County, in northwestern IN. It is a good idea to scout all cucurbits if you have not yet seen downy mildew in your area, and maintain a protectant fungicide program. Keep in mind that on squash and pumpkins, powdery mildew can look like downy mildew in the early stages before the white powdery mycelium is seen. Many of the fungicides used to manage these two very different diseases are fairly specific to either one, so be sure to have an accurate diagnosis.